Pinkie Pie is a mythic Legendary Creature — Pony card from Secret Lair Drop (SLD), collector number 1539. Current market price: $35.79 (foil $44.55), TCGplayer market prices via Scryfall.
Whenever you cast a spell with a smile in its art, create a tapped Treasure token. Everypony's Invited — Your party consists of each creature you control, and your party is always full.